1. Field of the Invention
The present invention relates to a system and a method for detecting aerosol particles in the atmosphere and counting the aerosol particles, and more particularly, to a system and a method for counting the detected aerosol particles with respect to each particle size.
2. Description of the Related Art
In the atmosphere, “aerosol particles” which are fine liquid or solid particles are suspended. As these aerosol particles, the ISO 15900:2009 standard for differential electrical mobility analysis for aerosol particles targets at aerosol particles whose particle size is 1 nm to 1 .mu.m. To count the aerosol particles having several nm to 1 .mu.m particle sizes, an aerosol particle measuring device is used. The aerosol particle measuring device includes, for example, a differential mobility analyzer (DMA) and a condensation particle counter (CPC), or the DMA and a Faraday cup aerosol electrometer (FCAE). The CPC or the FCAE measures the aerosol particles classified out by the DMA, whereby it is possible to count the aerosol particles with respect to each particle size by using the result of the measurement.
In the case where the DMA is used for the classifying, the aerosol particles include not only singly charged aerosol particles whose particle size is relatively small but also multiply (doubly, triply, . . . ) charged aerosol particles whose particle size is relatively large. Therefore, in the measurement, it is assumed that the aerosol particles classified out by the DMA are singly charged and a lognormal distribution holds true in a relation between the particle size and quantity, and the counting result is corrected regarding the quantity of the multiply charged aerosol particles and then particle size distribution is calculated. In the correction, an approximate expression of Wiedensohler or the like is employed as an existence probability of charged number.
When aerosol in the atmosphere is measured, it is generally assumed that the particle distribution is the lognormal distribution, but actually, this is not always the case. Further, in the ordinary measurement method, since the measurement is based on the assumption that aerosol particles are singly charged, it is not known how many multiply charged aerosol particles different in particle size are actually included, which makes it difficult to obtain an accurate result.